Find Trend and Plunge from Map Trace and Elevation

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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This is a simple problem, best illustrated by example. Note that unlike strike, plunge has a unique direction. A plane striking 058 is the same as one striking 238, but a line trending 058 is not the same as one trending 238. Trend is the direction down the plunge of the line.

1. Find the trend and plunge of the borehole shown. The elevation points are meters above sea level, so the plunge is northwest.

2. The trend is merely the azimuth of the map trace. Note that a trend of 328 is not the same as a trend of 148! Unlike strike, trend is a unique direction.

3. Determine spacing of elevation points using a cross-section or trigonometry.

4. Final result. We could state the plunge as 23 NW to reinforce the direction, but it's not necessary.


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Created 5 January 1999, Last Update Last Update 30 January 2012
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